US9144796B1 - Method of applying washcoat to monolithic substrate - Google Patents

Method of applying washcoat to monolithic substrate Download PDF

Info

Publication number
US9144796B1
US9144796B1 US12/752,753 US75275310A US9144796B1 US 9144796 B1 US9144796 B1 US 9144796B1 US 75275310 A US75275310 A US 75275310A US 9144796 B1 US9144796 B1 US 9144796B1
Authority
US
United States
Prior art keywords
washcoat composition
washcoat
substrate monolith
face
monolith
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active, expires
Application number
US12/752,753
Inventor
Christopher John Bennett
John P. Coll
Debnath DE
Andrea Hawkins
Wendy MANNING
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Johnson Matthey PLC
Original Assignee
Johnson Matthey PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Johnson Matthey PLC filed Critical Johnson Matthey PLC
Priority to US12/752,753 priority Critical patent/US9144796B1/en
Assigned to JOHNSON MATTHEY PUBLIC LIMITED COMPANY reassignment JOHNSON MATTHEY PUBLIC LIMITED COMPANY ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: COLL, JOHN P., DE, Debnath, MANNING, Wendy, HAWKINS, ANDREA, BENNETT, CHRISTOPHER JOHN
Application granted granted Critical
Publication of US9144796B1 publication Critical patent/US9144796B1/en
Active legal-status Critical Current
Adjusted expiration legal-status Critical

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
    • G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/63—Platinum group metals with rare earths or actinides
    • B01J35/56—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating
    • B01J37/0219—Coating the coating containing organic compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating
    • B01J37/0228—Coating in several steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0234—Impregnation and coating simultaneously
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/024—Multiple impregnation or coating
    • B01J37/0244—Coatings comprising several layers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
    • G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
    • G01N24/088—Assessment or manipulation of a chemical or biochemical reaction, e.g. verification whether a chemical reaction occurred or whether a ligand binds to a receptor in drug screening or assessing reaction kinetics
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/30—Sample handling arrangements, e.g. sample cells, spinning mechanisms
    • G01R33/307—Sample handling arrangements, e.g. sample cells, spinning mechanisms specially adapted for moving the sample relative to the MR system, e.g. spinning mechanisms, flow cells or means for positioning the sample inside a spectrometer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/22—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to internal surfaces, e.g. of tubes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/46—NMR spectroscopy
    • G01R33/465—NMR spectroscopy applied to biological material, e.g. in vitro testing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S502/00—Catalyst, solid sorbent, or support therefor: product or process of making
    • Y10S502/514—Process applicable either to preparing or to regenerating or to rehabilitating catalyst or sorbent
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S502/00—Catalyst, solid sorbent, or support therefor: product or process of making
    • Y10S502/52719—Monolith with specified shape or dimension of cell opening, e.g. honeycomb, rings

Definitions

  • the present invention relates to a washcoat composition, in particular a washcoat composition for coating a substrate monolith, and to a method of coating a substrate monolith with such washcoat composition.
  • WO 99/47260 discloses an apparatus for coating a substrate monolith comprising a plurality of substantially parallel channels extending from a first end face to a second end face thereof, which apparatus comprising means for dosing a pre-determined quantity of a liquid component, such quantity being such that may be substantially wholly retained within a substrate monolith to be coated, liquid component containment means locatable on the top of the substrate monolith to receive said quantity of liquid component, and pressure means such as over-pressure or a vacuum for transferring the liquid component from the containment means into at least a portion of the substrate monolith.
  • the method may be used to part-coat the substrate monolith in a first axial direction from one end face, before the part-coated substrate monolith is turned and the remainder of the substrate monolith is coated from the opposite end face in the same axial direction.
  • the rheology of the liquid component may be such that it does not begin to enter the cells of the substrate monolith until pressure or vacuum is applied.
  • the apparatus and method of the invention may provide plug flow of the dispensed quantity of liquid into the support.
  • “Rheology” may be defined as a material's response to a stress applied on the material during production, processing and/or application. Rheology measures the change in viscosity of a substance under changing shear rates, or a change in viscosity over time, at a constant shear rate.
  • a washcoat composition comprising a liquid phase, at least one polysaccharide rheology modifier and either one or both of (a) suspended metal oxide particles and (b) at least one metal salt solute in the liquid phase, wherein the rheology of the washcoat composition is pseudoplastic.
  • FIG. 1 is a graph in which the viscosity of a solution of scleroglucan in deionised water is plotted against temperature
  • FIG. 2 is a graph in which the viscosity of a solution of guar gum in deionised water is plotted against temperature
  • FIG. 3 is a graph in which the viscosity of a washcoat composition comprising a solution of Ce:Zr nitrate and scleroglucan is plotted against temperature;
  • FIG. 4 is a graph in which the viscosity of a washcoat composition comprising a solution of Ce:Zr nitrate and hydroxyethyl cellulose is plotted against temperature;
  • FIG. 5 is a graph in which the which the viscosity of a washcoat composition comprising colloidal alumina and scleroglucan is plotted against temperature
  • FIG. 6 is a graph in which the viscosity of a washcoat composition comprising colloidal alumina and hydroxyethyl cellulose is plotted against temperature.
  • washcoat composition herein is used to refer to either compositions containing metal oxide particles or, in the alternative, compositions that do not contain metal oxide particles.
  • liquid phase is meant to include liquids, solutions, suspensions, colloids, sols, emulsions, and gels.
  • the rheology, or flow behaviour, of a material may be classified as Newtonian and non-Newtonian.
  • Newtonian flow describes a material that exhibits no change in viscosity with increasing shear rate.
  • a classical example of a compound with Newtonian behaviour is water.
  • Non-Newtonian flow includes pseudoplastic, thixotropic or dilatant flow, based on the measured response of the material to a known shear rate, compared to classical models.
  • Pseudoplastic flow describes a system that exhibits a reduction in viscosity with increasing shear rate. The viscosity will recover as the shear is removed; though it may not follow the same viscosity profile as exhibited with increasing shear. This type of flow is also referred to as “shear thinning”. In contrast the viscosity characteristics of a pseudoplastic material, the viscosity of a thixotropic fluid decreases over time at a constant shear rate.
  • Rheology modifiers useful in the present invention provide the washcoat with pseudoplastic properties although the modifiers may also impart thixotropic properties under certain conditions.
  • pseudoplastic flow is a particular advantage in the method disclosed in WO 99/47260 because, when the pressure means is actuated it generates a shear stress in a pseudoplastic gel-like washcoat composition deposited in the containment means on top of an upper face of the substrate monolith, which pressure means reduces the viscosity of the washcoat composition and enables it to be drawn into the channels of the monolith substrate and coating the channels by plug flow.
  • the quantity of washcoat composition is selected so that when plug flow breaks down, the washcoat composition is substantially wholly retained within the channels of the substrate monolith.
  • the pseudoplastic nature of the washcoat composition means that it returns to a gel-like consistency, thus holding the washcoat composition where it has been coated in the channels of the substrate monolith.
  • rheology modifiers in compositions comprising a liquid phase and a suspension of particulate metal oxides is known in printing inks.
  • printer inks typically exhibit rheopectic-type behaviour—that is, they become more viscous when subjected to shear stress (e.g., shaking).
  • shear stress e.g., shaking
  • alternative applications may be further distinguished by any one or more of a number of the following characteristics of a washcoat composition. For example, depending on the application of the substrate monolith e.g.
  • the metal oxide particles may have a D50 of 0.1-6.0 ⁇ m, such as 3.0-5.0 ⁇ m or 0.1-2.0 ⁇ m; or a D90 of ⁇ 15.0 ⁇ m, such as less than 13.0 ⁇ m, e.g. less than 12.0 ⁇ m or less than 5.0 ⁇ m; a solids content of 3-40 wt %, such as 15-40%, 30-40% or 3-15%; the pH of the washcoat is acidic, i.e.
  • ⁇ pH 7 such as ⁇ pH 6.0, ⁇ pH 5.0, ⁇ pH 4.0, ⁇ pH 3.0, ⁇ pH 2.0, ⁇ pH 1.5 or ⁇ pH 1.0; or the liquid phase comprises water, e.g. 90% water, such as >95% water or >98% water—in other words, preferred rheology modifiers are tolerant to low pH; they will still gel the composition.
  • Metal oxide particles can be measured using a suitable instrument, e.g. a Malvern LS2000 particle sizer using the Mie optical model.
  • preferred rheology modifiers for use in the present invention are resistant to multivalent ions at such low pH. Accordingly, the preferred rheology modifiers are resistant (they will still gel the composition) to one or more multivalent cations of any of the metal salts listed hereinbelow, including: Pt 2+ , Pt 4+ , Pt 6+ , Pd 2+ , Rh 3+ , Cu 2+ , Fe 2+ , Fe 3+ , Ni 2+ , Ni 3+ , Co 2+ , Co 3+ , Ce 4+ , Zr 4+ , Y 3+ , Pr 3+ , La 3+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , molybdates such as MO 7 O 24 6 ⁇ and Mo 8 O 26 4 ⁇ and tungstate (WO 4 2 ⁇ ).
  • the metal oxide for use in the washcoat composition may be selected from the group consisting essentially of alumina, ceria, zirconia, ceria-zirconia, silica, silica-alumina, titania, a zeolite or mixtures of any two or more thereof.
  • the definition “consisting essentially” anticipates the presence of minor amounts of promoters e.g. barium and/or stabilisers, e.g. lanthanum stabilised alumina, that may affect the washcoat composition, but do not function as a metal catalyst per se.
  • each metal in the metal salt of the washcoat composition according to the invention can be selected from the group consisting of Group IA (e.g. potassium, caesium), Group IB (e.g. copper, silver, gold), Group IIA (e.g. magnesium, calcium, strontium, barium), Group IIIB (e.g. yttrium, lanthanides such as cerium and praseodymium), Group IVB (e.g. zirconium), Group VB (e.g. vanadium), Group VIB (e.g. molybdenum, tungsten), Group VIIB (e.g. manganese) and Group VIII (e.g. iron, ruthenium, nickel, palladium, rhodium, platinum, palladium).
  • Group IA e.g. potassium, caesium
  • Group IB e.g. copper, silver, gold
  • Group IIA e.g. magnesium, calcium, strontium, barium
  • Group IIIB e.g. yt
  • each metal in the metal salt is a transition metal, wherein the transition metal can be a precious metal (i.e. Au, Ag, Pt, Pd, Rh, Ir, Os, Ru etc.), Cu, Fe, Mn, Ce, Zr, W or V.
  • each precious metal is a platinum group metal, i.e. Pt, Pd, Rh, Ir, Os, Ru etc. Suitable combinations of platinum group metals, depending on the application, include Pt/Rh for NO x absorbers and Pt/Pd for diesel oxidation catalysts (DOCs).
  • DOCs diesel oxidation catalysts
  • the invention extends to the possibility of pre-fixing one or more of the abovementioned metals in the metal salts on the metal oxide particles prior to forming the washcoat composition.
  • Pre-fixed metals may be present as elemental metal or as a metal compound, such as an oxide.
  • Methods of pre-fixing include impregnating the metal oxide particles with a suitable salt solution followed by drying a calcining (firing) step.
  • the washcoat composition can comprise metal pre-fixed on the metal oxide particles and at least one metal salt solute in the liquid phase.
  • the coated substrate monoliths can be used in a wide range of applications, including treating industrial effluent and “off-gas” and for treating emissions from stationary source and mobile applications such as diesel or gasoline engines and gas turbines. Accordingly, the substrate monoliths and the components in the washcoat components may be selected dependent on the desired application, e.g. selective catalytic reduction using nitrogenous reductants or hydrocarbon reductants, NO x , absorption, oxidation such as diesel oxidation, three-way catalysis etc.
  • the rheology modifier for use in the present invention preferably comprises one or more polysaccharide and can be a naturally occurring product or derived from a naturally occurring product, or a synthetic product. It can be ionic, such as anionic, or non-ionic.
  • the rheology modifier comprises at least one polysaccharide selected from the group consisting of a galactomannan gum, xanthan gum, curdlan, Schizophyllan, Scleroglucan, Diutan gum, Welan gum and mixtures of any two or more thereof.
  • the rheology modifier preferably comprises Scleroglucan and/or Schizophyllan, with Scleroglucan being particularly preferred.
  • Galactomannans are naturally occurring polysaccharides consisting of a mannose backbone with galactose side groups (more specifically, a (1-4)-linked beta-D-mannopyranose backbone with branchpoints from their 6-positions linked to alpha-D-galactose, i.e. 1-6-linked alpha-D-galactopyranose) obtainable from the beans of certain plants.
  • galactomannans include fenugreek gum (mannose:galactose ⁇ 1:1), guar gum (mannose:galactose ⁇ 2:1), tara gum (mannose:galactose ⁇ 3:1) and locust bean gum or carob gum (mannose:galactose ⁇ 4:1).
  • the backbone of the polysaccharide chain of xanthan gum consists of two ⁇ -D-glucose units linked through the 1 and 4 positions.
  • the side chain consists of two mannose and one glucuronic acid, so the chain consists of repeats of five sugar units.
  • Dissolved xanthan chains also assume a rod-like double helix structure. It is produced by a process involving fermentation of glucose or sucrose by the Xanthomonas campestris bacterium.
  • Curdlan is naturally occurring polysaccharide produced by Agrobacterium biobar. It consists of Beta-1,3-glucan, a high molecular weight polymer.
  • Schizophyllan is a neutral, extracellular polysaccharide produced by the fungus Schizophyllan commune , consisting of a 1,3- ⁇ -D-linked backbone of glucose residues with 1,6- ⁇ -D-glucosyl side groups.
  • Scleroglucan is a water-soluble natural non-ionic polymer produced by the fermentation of the filamentous fungi sclerotium rofsii .
  • the chemical structure consists of beta 1,3-D-glucose residues with one beta-1,6-D-glucose side chain every three main residues. Dissolved scleroglucan chains also assume a rod-like triple helical structure, in which the glucose residues sit on the outside.
  • Welan gum is an anionic microbial polysaccharide produced by a species of Alcaligenes .
  • the structure is based on repeating glucose, rhamnose and glucuronic acid units but with a single side chain of either an ⁇ -L-rhamnopyranosyl or an ⁇ -L-mannopyranosyl unit linked (1-3) to the 4-O-substituted ⁇ -D-glucopyranosyl unit in the backbone.
  • Diutan gum is a biopolymer very similar to Welan gum. Welan gum and diutan gum also assume the rod-like triple helical configuration seen in scleroglucan.
  • Scleroglucan, welan gum and diutan gum have a number of interesting properties that make them potentially very useful to the methods disclosed, e.g. in WO 99/47260. These include that they are relatively stable, e.g. relative to xanthan gums, in low pH, e.g. ⁇ pH 3.0, ⁇ pH 2.0, ⁇ pH 1.5 or ⁇ pH 1.0; their viscosity increases with temperature; and their viscosity increases with time in the absence of applied shear stress.
  • the polysaccharide rheology modifier is a starch, a cellulose or an alginate or is derived from a starch, a cellulose (i.e. cellulosic) or an alginate, though these rheology modifiers do not share all of the properties of scleroglucan, welan gum and diutan gum, e.g. hydroxyethyl cellulose may degrade on heating even at neutral or basic pH.
  • the cellulosic rheology modifier may be selected from the group consisting of carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose and ethyl hydroxyethyl cellulose.
  • the polysaccharide rheology modifier may be an associative rheology modifier, cellulosic examples of which include hydrophobically modified hydroxyethyl cellulose or hydrophobically modified ethyl hydroxyethyl cellulose.
  • cellulosic rheology modifiers such as hydroxy methyl cellulose, behave differently in a washcoat composition than in water. For example, we have seen that hydroxy methyl cellulose becomes associative in a washcoat composition, e.g. at acid pH, but not in deionised water. This is particularly surprising since hydroxy methyl cellulose is generally not regarded as associative.
  • the at least one rheology modifier can be a mixture of guar gum and xanthan gum.
  • Rheology modifiers are generally present in the washcoat composition according to the invention at up to 5.0 wt % per volume, such as up to 4.0 wt % per volume, up to 3.0 wt % per volume, 2.0 wt % per volume, 1.5 wt % per volume and 1.0 wt % per volume.
  • substrate monolith As defined herein, “substrate monolith”, “substrate” or “monolith” is a structure comprising a plurality of generally parallel channels extending in a generally axial direction through at least part of the structure and, in certain preferred embodiments, is a ceramic or metal honeycomb.
  • the channels can have any cross sectional shape e.g. square, triangular etc.
  • the structure can be the so-called “flow through” arrangement, where both inlet and outlet ends of the channels are open to fluid flow or the structure can be a filter.
  • Various filter arrangements are known, including the so-called wall flow filter, wherein each channel has a plug at one end and the opposite end is open, with any pair of adjacent channels having plugs at opposite channel ends.
  • the term “filter” herein also includes partial filters, such as those disclosed in EP 1276549 and EP 1057519 (the entire contents of both documents being incorporated herein by reference).
  • the invention provides the use of at least one polysaccharide rheology modifier (as described hereinabove) in the manufacture of a rheologically pseudoplastic washcoat composition for coating a substrate monolith, wherein the washcoat composition comprises a liquid phase and either one or both of (a) suspended metal oxide particles and (b) at least one metal salt solute in the liquid phase, wherein the rheology of the washcoat composition is pseudoplastic.
  • each coating step may need to be followed immediately by a drying step and optionally also by a firing (i.e. calcining) step.
  • the use of the polysaccharide rheology modifiers disclosed herein can reduce the number of process steps involved in obtaining the final coated substrate monolith, i.e. they enable a substrate monolith to be part-coated in a first axial direction from one end face, before the part-coated substrate monolith is turned and the remainder of the substrate monolith is coated from the opposite end face in the same axial direction without a drying step between a first washcoat application and a second washcoat application.
  • rheology modifiers comprising polysaccharide chains that assume rod-like double and particularly triple helices when dissolved—such as scelroglucan, welan gum and diutan gum—are particularly useful in the method disclosed in WO 99/47260.
  • rheology modifiers in particular, it is possible to coat a substrate monolith from one end by application of shear stress using the pressure means and to turn the substrate monolith without first drying the first part-coating before the substrate monolith is coated from the opposite end face. That is, pressure means is applied across an undried first part-coating.
  • One feature of the selected rheology modifiers that facilitates this is that they make the washcoat strongly pseudoplastic, i.e. they can increase in washcoat viscosity rapidly producing a strong gelled-structure (due to triple helical structures of thickeners) with time upon the cessation of the applied shear stress.
  • the use of the above rheology modifiers enables a second washcoat layer to be applied over the dried first washcoat layer, i.e. it may not be necessary first to fire (calcine) the first washcoat layer before overlaying the first washcoat layer with a second washcoat layer.
  • the drying step sufficiently increases the viscosity of the washcoat composition of the first layer.
  • the feature that the selected polysaccharide rheology modifiers, e.g. scleroglucan, welan gum and diutan gum, are stable in low pH is also an advantage for washcoating systems that require acid pH, e.g. to impregnate anionic platinum group metal salts onto acidic metal oxide particles, e.g. alumina, silica-alumina and titania.
  • acidic metal oxide particles e.g. alumina, silica-alumina and titania.
  • relatively low pH washcoat compositions e.g. less than pH 2.0
  • polysaccharide rheology modifiers that assume a rod-like triple helical structure when dissolved in water retain their viscosity (tested on a Brookfield viscometer) when stored for over two months.
  • washcoat compositions one comprising metal salts (Ce:Zr nitrate) and the other comprising a slurry of metal oxide particles (alumina). It was also observed, that these preferred rheology modifiers are resistant to multivalent cations (such as Ce 4+ and Zr 4+ ) at the low pHs tested.
  • polysaccharide rheology modifiers in general, and these selected rheology modifiers in particular, is advantageous in that they can reduce substantially the number of process steps necessary to obtain a coated substrate monolith.
  • a method for coating a substrate monolith having a plurality of channels and having a first end, wherein said first end comprises a plurality of channel openings comprising: (a) contacting a predetermined quantity of a rheologically pseudoplastic washcoat with said first end, wherein said washcoat comprises a liquid phase, a polysaccharide rheological modifier, and either one or both of (i) suspended metal oxide particles and (ii) at least one metal salt solute in the liquid phase; (b) applying a vacuum and/or positive pressure to said washcoat, wherein said applying said vacuum and/or positive pressure decreases the viscosity of the washcoat; (c) coating at least a portion of said channels with said washcoat; and (d) removing said vacuum and/or positive pressure from said washcoat.
  • steps (a), (b), (c), and (d) of this method are performed in the order described above.
  • the invention provides a method of coating a substrate monolith comprising a first end face and a second end face and a plurality of substantially parallel channels extending from the first end face to the second end face with a washcoat composition, which method comprising the steps of:
  • step (d) rotating a part-coated substrate monolith resulting from step (c) so that the second end face is located at the top;
  • the product of step (e) comprises a substrate monolith coated substantially uniformly with a first layer of the washcoat composition.
  • step (e) can be subjected to a drying step following which it can be fired (calcined) or alternatively the dried product of step (e) can be coated with a second washcoat layer by repeating steps (a) to (e) inclusive before the two layer product can be fired (calcined).
  • the washcoat composition comprises a platinum group metal, which can be present as a salt solution or pre-fixed to the metal oxide particles.
  • polysaccharide rheology modifiers that assume a rod-like triple helical structure when dissolved in water, e.g. Scleroglucan, Diutan gum or Welan gum, for reasons explained hereinabove.
  • the method according to the invention provides a number of very useful advantages where expensive precious metals are used. These include the more rigorous control of precious metals within the method, reducing losses.
  • the present invention allows washcoat compositions comprising precious metal salts to be applied as a separate step to a washcoat layer(s) containing metal oxide particles that has been laid down in previous step, rather than combining precious metal salts and metal oxide particles in the same washcoat composition (although this is still possible according to the present invention).
  • An advantage is that washcoat compositions comprising precious metal salts and no metal oxide particles are more easily analysed, e.g.
  • ICP-ES Inductively Coupled Plasma Emission Spectroscopy
  • washcoat compositions comprising precious metal salts and metal oxide particles (“slurries”) where e.g. X-Ray Fluorescence (XRF) can be used, which requires the preparation of “homemade” standards for slurries.
  • XRF X-Ray Fluorescence
  • a precious metal application step can be separated from a step of coating the monolith substrate with a washcoat composition containing metal oxide particles, a problem of flushing lines to recover precious metals when the washcoat composition is changed, e.g. from a rhodium containing washcoat composition to a palladium-containing washcoat composition, can be reduced or avoided.
  • this reduces the amount of time during which production apparatus is inactive while the lines are being flushed (“downtime”).
  • downtime the amount of time during which production apparatus is inactive while the lines are being flushed
  • less rinse water is used for line flushing. The method according to the invention reduces or avoids this problem.
  • the viscosity (cPs) of a representative low pH (pH ⁇ 0.8) washcoat composition comprising a solution of Ce:Zr nitrate and scleroglucan, guar gum or hydroxyethyl cellulose ((Natrosol MR250) no particulate metal oxide) was tested using a Brookfield Viscometer in 10° C. increments. Illustrative results trends for scleroglucan and hydroxyethyl cellulose are set out in Tables 3 and 4. The results are also shown graphically in FIGS. 3 and 4 respectively. Guar gum would not polymerize in the low pH solution.
  • the viscosity (cPs) of a representative washcoat composition containing a particulate metal oxide comprising a colloidal alumina doped with citric acid and platinum nitrate at a pH ⁇ 1.5 was tested using a Brookfield Viscometer in 10° C. increments.
  • the illustrative results trend for scleroglucan and guar gum are set out in Tables 5 and 6 and is also shown in FIGS. 5 and 6 .
  • scleroglucan and guar gum worked well for thickening washcoat composition containing particulate metal oxide both at room temperature and when heated to typical drying temperatures.
  • the guar gum showed a decrease in viscosity between 30-50° C., but viscosity recovered at higher temperatures. This was observed on two separate samples with two different concentrations of guar gum (results not shown).
  • Scleroglucan also showed a loss in viscosity between 40-60° C. (results not shown). However, when the test was repeated at a higher polymer concentration, the loss in viscosity was much less pronounced.
  • scleroglucan is a stable rheology modifier in the washcoat composition systems tested.
  • Catalysed wall-flow diesel particulate filters having a total length of 12 inches (30.48 cm) were prepared using the method disclosed in WO 99/47260 using the washcoat compositions of Example 2 with the objective of achieving the washcoat component loadings on the catalysed diesel particulate filter set out in Table 9.
  • Positions 1 and 2 of 5 in an automated apparatus were prepared targeting 50% dose lengths measured from the top down.
  • the two samples were then transferred into a dryer and dried for 45 minutes at 100° C. These parts were monitored for solution migration using 3-dimensional X-ray throughout the drying process.
  • the washcoat composition containing xanthan gum migrated from 50% of the filter length down to approximately 75% of the filter length, whereas the scleroglucan-containing sample at position 2 showed virtually no signs of solution migration during the drying step.
  • Positions 3-5 were prepared using the colloidal alumina washcoat composition of Example #3.
  • a target dose length of 75% of the total length of the filter was intended (approx. 7 inches or 17.78 cm). Samples were dried at 100° C. for 60 minutes and monitored for washcoat migration.
  • the filter sample at position #3 using xanthan gum began to migrate on heating to the bottom of the filter in a funnel shaped pattern.
  • the centre of the filter showed a 6 inch (15.24 cm) diameter drainage pattern after 30 minutes of drying. After 60 minutes the drainage increased to a 10 inch (25.4 cm) diameter with a 3 inch (7.62 cm) spot which migrated completely through the filter to the opposite end face creating a 3 inch (7.62 cm) diameter spot with cell blockage.
  • the position #1 sample showed poor thermal stability: gelled solution migration was uncontrolled after the filter temperature exceeded 40° C.
  • Position #5 using guar gum also showed good rheology characteristics during the drying cycle, although there was more washcoat migration during drying than for the #4 sample, the concentration of guar gum required for colloidal alumina slurries was significantly less than for scleroglucan.
  • Nitric acid was added to 600 g of deionised water to lower the pH to 1.2. 266 g of citric acid were then added, resulting in a pH of 1.03. 4.2 g of a commercially available xanthan gum (Vanzan®) were then successively dissolved in the solution. The resulting solution had a viscosity of 2000 cPs (measured by a Brookfield viscometer) and a pH of 1.05.

Abstract

A method of coating substrate monoliths is disclosed. The method comprises locating a containment means on top of the first end face of the monolith; and dosing a predetermined quantity of washcoat composition comprising a liquid phase, at least one polysaccharide rheology modifier and at least one of (i) a suspension of metal oxide particles into the containment means; and (ii) at least one metal salt solute in the liquid phase. The locating step may occur before or after the dosing step. Pressure is applied to the washcoat composition to generate shear stress and to transfer an entirety of washcoat composition into the channels of the monolith by plug flow. Substantially all of the predetermined quantity is retained within the monolith. The part-coated monolith is then rotated so that the second end face is located at the top, and the first three steps are repeated without drying the part-coated monolith.

Description

CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority from U.S. Provisional Application No. 61/165,540, filed Apr. 1, 2009, which is incorporated herein by reference in its entirety for all purposes.
FIELD OF THE INVENTION
The present invention relates to a washcoat composition, in particular a washcoat composition for coating a substrate monolith, and to a method of coating a substrate monolith with such washcoat composition.
BACKGROUND OF THE INVENTION
WO 99/47260 (the entire contents of which is incorporated herein by reference) discloses an apparatus for coating a substrate monolith comprising a plurality of substantially parallel channels extending from a first end face to a second end face thereof, which apparatus comprising means for dosing a pre-determined quantity of a liquid component, such quantity being such that may be substantially wholly retained within a substrate monolith to be coated, liquid component containment means locatable on the top of the substrate monolith to receive said quantity of liquid component, and pressure means such as over-pressure or a vacuum for transferring the liquid component from the containment means into at least a portion of the substrate monolith. An important characteristic of the disclosed apparatus and method is that substantially all of the liquid is retained within the substrate monolith, ensuring an even distribution in the desired pattern, and ensuring that there is no significant excess liquid requiring recycling. This feature is particularly important to reduce or prevent losses of the liquid component, and any precious metals contained therein. In a preferred embodiment wherein substantially all of the liquid component is retained within the substrate monolith, the method may be used to part-coat the substrate monolith in a first axial direction from one end face, before the part-coated substrate monolith is turned and the remainder of the substrate monolith is coated from the opposite end face in the same axial direction.
The description mentions that for certain coating components, the rheology of the liquid component may be such that it does not begin to enter the cells of the substrate monolith until pressure or vacuum is applied. In particular, the apparatus and method of the invention may provide plug flow of the dispensed quantity of liquid into the support.
“Rheology” may be defined as a material's response to a stress applied on the material during production, processing and/or application. Rheology measures the change in viscosity of a substance under changing shear rates, or a change in viscosity over time, at a constant shear rate.
SUMMARY OF THE INVENTION
We have now identified a family of rheology modifiers for use in the apparatus and the method disclosed in WO 99/47260, which provides a range of particular advantages in use.
According to a first aspect, there is provided a washcoat composition comprising a liquid phase, at least one polysaccharide rheology modifier and either one or both of (a) suspended metal oxide particles and (b) at least one metal salt solute in the liquid phase, wherein the rheology of the washcoat composition is pseudoplastic.
BRIEF DESCRIPTION OF THE DRAWING
In order that the invention may be more fully understood, the following Examples are provided by way of illustration only and with reference to the accompanying drawings, in which:
FIG. 1 is a graph in which the viscosity of a solution of scleroglucan in deionised water is plotted against temperature;
FIG. 2 is a graph in which the viscosity of a solution of guar gum in deionised water is plotted against temperature;
FIG. 3 is a graph in which the viscosity of a washcoat composition comprising a solution of Ce:Zr nitrate and scleroglucan is plotted against temperature;
FIG. 4 is a graph in which the viscosity of a washcoat composition comprising a solution of Ce:Zr nitrate and hydroxyethyl cellulose is plotted against temperature;
FIG. 5 is a graph in which the which the viscosity of a washcoat composition comprising colloidal alumina and scleroglucan is plotted against temperature; and
FIG. 6 is a graph in which the viscosity of a washcoat composition comprising colloidal alumina and hydroxyethyl cellulose is plotted against temperature.
 DETAILED DESCRIPTION OF THE INVENTION
It will be appreciated that the art sometimes refers to a “washcoat” as a “slurry” comprising metal oxide particles. For the avoidance of any doubt “washcoat composition” herein is used to refer to either compositions containing metal oxide particles or, in the alternative, compositions that do not contain metal oxide particles.
As used herein, the term “liquid phase” is meant to include liquids, solutions, suspensions, colloids, sols, emulsions, and gels.
The rheology, or flow behaviour, of a material may be classified as Newtonian and non-Newtonian. Newtonian flow describes a material that exhibits no change in viscosity with increasing shear rate. A classical example of a compound with Newtonian behaviour is water. Non-Newtonian flow includes pseudoplastic, thixotropic or dilatant flow, based on the measured response of the material to a known shear rate, compared to classical models.
Pseudoplastic flow describes a system that exhibits a reduction in viscosity with increasing shear rate. The viscosity will recover as the shear is removed; though it may not follow the same viscosity profile as exhibited with increasing shear. This type of flow is also referred to as “shear thinning”. In contrast the viscosity characteristics of a pseudoplastic material, the viscosity of a thixotropic fluid decreases over time at a constant shear rate. Rheology modifiers useful in the present invention provide the washcoat with pseudoplastic properties although the modifiers may also impart thixotropic properties under certain conditions.
It can be seen that pseudoplastic flow is a particular advantage in the method disclosed in WO 99/47260 because, when the pressure means is actuated it generates a shear stress in a pseudoplastic gel-like washcoat composition deposited in the containment means on top of an upper face of the substrate monolith, which pressure means reduces the viscosity of the washcoat composition and enables it to be drawn into the channels of the monolith substrate and coating the channels by plug flow. The quantity of washcoat composition is selected so that when plug flow breaks down, the washcoat composition is substantially wholly retained within the channels of the substrate monolith. Moreover, since the shear stress is substantially removed when plug flow breaks down and/or when the pressure means is deactivated, the pseudoplastic nature of the washcoat composition means that it returns to a gel-like consistency, thus holding the washcoat composition where it has been coated in the channels of the substrate monolith.
The use of rheology modifiers in compositions comprising a liquid phase and a suspension of particulate metal oxides is known in printing inks. However, printer inks typically exhibit rheopectic-type behaviour—that is, they become more viscous when subjected to shear stress (e.g., shaking). Moreover, such alternative applications may be further distinguished by any one or more of a number of the following characteristics of a washcoat composition. For example, depending on the application of the substrate monolith e.g. a filter or a flow-through substrate monolith for diesel or gasoline applications, the metal oxide particles may have a D50 of 0.1-6.0 μm, such as 3.0-5.0 μm or 0.1-2.0 μm; or a D90 of <15.0 μm, such as less than 13.0 μm, e.g. less than 12.0 μm or less than 5.0 μm; a solids content of 3-40 wt %, such as 15-40%, 30-40% or 3-15%; the pH of the washcoat is acidic, i.e. <pH 7, such as <pH 6.0, <pH 5.0, <pH 4.0, <pH 3.0, <pH 2.0, <pH 1.5 or <pH 1.0; or the liquid phase comprises water, e.g. 90% water, such as >95% water or >98% water—in other words, preferred rheology modifiers are tolerant to low pH; they will still gel the composition. Metal oxide particles can be measured using a suitable instrument, e.g. a Malvern LS2000 particle sizer using the Mie optical model.
Another aspect of pH tolerance is that preferred rheology modifiers for use in the present invention are resistant to multivalent ions at such low pH. Accordingly, the preferred rheology modifiers are resistant (they will still gel the composition) to one or more multivalent cations of any of the metal salts listed hereinbelow, including: Pt2+, Pt4+, Pt6+, Pd2+, Rh3+, Cu2+, Fe2+, Fe3+, Ni2+, Ni3+, Co2+, Co3+, Ce4+, Zr4+, Y3+, Pr3+, La3+, Mg2+, Ca2+, Sr2+, Ba2+, molybdates such as MO7O24 6− and Mo8O26 4− and tungstate (WO4 2−).
The metal oxide for use in the washcoat composition may be selected from the group consisting essentially of alumina, ceria, zirconia, ceria-zirconia, silica, silica-alumina, titania, a zeolite or mixtures of any two or more thereof. The definition “consisting essentially” anticipates the presence of minor amounts of promoters e.g. barium and/or stabilisers, e.g. lanthanum stabilised alumina, that may affect the washcoat composition, but do not function as a metal catalyst per se.
Preferably, each metal in the metal salt of the washcoat composition according to the invention can be selected from the group consisting of Group IA (e.g. potassium, caesium), Group IB (e.g. copper, silver, gold), Group IIA (e.g. magnesium, calcium, strontium, barium), Group IIIB (e.g. yttrium, lanthanides such as cerium and praseodymium), Group IVB (e.g. zirconium), Group VB (e.g. vanadium), Group VIB (e.g. molybdenum, tungsten), Group VIIB (e.g. manganese) and Group VIII (e.g. iron, ruthenium, nickel, palladium, rhodium, platinum, palladium).
In one embodiment, each metal in the metal salt is a transition metal, wherein the transition metal can be a precious metal (i.e. Au, Ag, Pt, Pd, Rh, Ir, Os, Ru etc.), Cu, Fe, Mn, Ce, Zr, W or V. In a preferred embodiment, each precious metal is a platinum group metal, i.e. Pt, Pd, Rh, Ir, Os, Ru etc. Suitable combinations of platinum group metals, depending on the application, include Pt/Rh for NOx absorbers and Pt/Pd for diesel oxidation catalysts (DOCs).
According to an embodiment of the invention, the invention extends to the possibility of pre-fixing one or more of the abovementioned metals in the metal salts on the metal oxide particles prior to forming the washcoat composition. Pre-fixed metals may be present as elemental metal or as a metal compound, such as an oxide. Methods of pre-fixing include impregnating the metal oxide particles with a suitable salt solution followed by drying a calcining (firing) step. It is also envisaged that the washcoat composition can comprise metal pre-fixed on the metal oxide particles and at least one metal salt solute in the liquid phase.
It will be appreciated that the coated substrate monoliths can be used in a wide range of applications, including treating industrial effluent and “off-gas” and for treating emissions from stationary source and mobile applications such as diesel or gasoline engines and gas turbines. Accordingly, the substrate monoliths and the components in the washcoat components may be selected dependent on the desired application, e.g. selective catalytic reduction using nitrogenous reductants or hydrocarbon reductants, NOx, absorption, oxidation such as diesel oxidation, three-way catalysis etc.
The rheology modifier for use in the present invention preferably comprises one or more polysaccharide and can be a naturally occurring product or derived from a naturally occurring product, or a synthetic product. It can be ionic, such as anionic, or non-ionic.
In one embodiment, the rheology modifier comprises at least one polysaccharide selected from the group consisting of a galactomannan gum, xanthan gum, curdlan, Schizophyllan, Scleroglucan, Diutan gum, Welan gum and mixtures of any two or more thereof. For embodiments wherein the washcoat requires low pH and high temperature stability, the rheology modifier preferably comprises Scleroglucan and/or Schizophyllan, with Scleroglucan being particularly preferred.
Galactomannans are naturally occurring polysaccharides consisting of a mannose backbone with galactose side groups (more specifically, a (1-4)-linked beta-D-mannopyranose backbone with branchpoints from their 6-positions linked to alpha-D-galactose, i.e. 1-6-linked alpha-D-galactopyranose) obtainable from the beans of certain plants. In order of increasing number of mannose:galactose, galactomannans include fenugreek gum (mannose:galactose ˜1:1), guar gum (mannose:galactose ˜2:1), tara gum (mannose:galactose ˜3:1) and locust bean gum or carob gum (mannose:galactose ˜4:1).
The backbone of the polysaccharide chain of xanthan gum consists of two β-D-glucose units linked through the 1 and 4 positions. The side chain consists of two mannose and one glucuronic acid, so the chain consists of repeats of five sugar units. Dissolved xanthan chains also assume a rod-like double helix structure. It is produced by a process involving fermentation of glucose or sucrose by the Xanthomonas campestris bacterium.
Curdlan is naturally occurring polysaccharide produced by Agrobacterium biobar. It consists of Beta-1,3-glucan, a high molecular weight polymer.
Schizophyllan is a neutral, extracellular polysaccharide produced by the fungus Schizophyllan commune, consisting of a 1,3-β-D-linked backbone of glucose residues with 1,6-β-D-glucosyl side groups.
Scleroglucan is a water-soluble natural non-ionic polymer produced by the fermentation of the filamentous fungi sclerotium rofsii. The chemical structure consists of beta 1,3-D-glucose residues with one beta-1,6-D-glucose side chain every three main residues. Dissolved scleroglucan chains also assume a rod-like triple helical structure, in which the glucose residues sit on the outside.
Welan gum is an anionic microbial polysaccharide produced by a species of Alcaligenes. The structure is based on repeating glucose, rhamnose and glucuronic acid units but with a single side chain of either an α-L-rhamnopyranosyl or an α-L-mannopyranosyl unit linked (1-3) to the 4-O-substituted β-D-glucopyranosyl unit in the backbone.
Diutan gum is a biopolymer very similar to Welan gum. Welan gum and diutan gum also assume the rod-like triple helical configuration seen in scleroglucan.
Scleroglucan, welan gum and diutan gum have a number of interesting properties that make them potentially very useful to the methods disclosed, e.g. in WO 99/47260. These include that they are relatively stable, e.g. relative to xanthan gums, in low pH, e.g. <pH 3.0, <pH 2.0, <pH 1.5 or <pH 1.0; their viscosity increases with temperature; and their viscosity increases with time in the absence of applied shear stress. For example, we have seen that for 1-1.5% solution of polysaccharide rheology modifiers that assume a rod-like triple helical structure when dissolved in water, viscosity increases by over 100% between 70 and 100° C., as measured on a Brookfield viscometer at 10° C. increments. It will be appreciated that in using a Brookfield viscometer, absolute viscosity readings may vary depending on what spindle number and/or conditions (most significantly spindle revolutions per minute (rpm)) are employed. However, regardless of what spindle or conditions are used, the trend of viscosity against temperature will be consistent for a given washcoat composition.
In an alternative embodiment, the polysaccharide rheology modifier is a starch, a cellulose or an alginate or is derived from a starch, a cellulose (i.e. cellulosic) or an alginate, though these rheology modifiers do not share all of the properties of scleroglucan, welan gum and diutan gum, e.g. hydroxyethyl cellulose may degrade on heating even at neutral or basic pH.
The cellulosic rheology modifier may be selected from the group consisting of carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose and ethyl hydroxyethyl cellulose.
The polysaccharide rheology modifier may be an associative rheology modifier, cellulosic examples of which include hydrophobically modified hydroxyethyl cellulose or hydrophobically modified ethyl hydroxyethyl cellulose. In our investigations, however, we have noticed that certain cellulosic rheology modifiers, such a hydroxy methyl cellulose, behave differently in a washcoat composition than in water. For example, we have seen that hydroxy methyl cellulose becomes associative in a washcoat composition, e.g. at acid pH, but not in deionised water. This is particularly surprising since hydroxy methyl cellulose is generally not regarded as associative.
It is possible according to the invention to use a single rheology modifier as defined herein, or a mixture or any two or more thereof. For example, in one embodiment, the at least one rheology modifier can be a mixture of guar gum and xanthan gum.
Rheology modifiers are generally present in the washcoat composition according to the invention at up to 5.0 wt % per volume, such as up to 4.0 wt % per volume, up to 3.0 wt % per volume, 2.0 wt % per volume, 1.5 wt % per volume and 1.0 wt % per volume.
As defined herein, “substrate monolith”, “substrate” or “monolith” is a structure comprising a plurality of generally parallel channels extending in a generally axial direction through at least part of the structure and, in certain preferred embodiments, is a ceramic or metal honeycomb. The channels can have any cross sectional shape e.g. square, triangular etc. The structure can be the so-called “flow through” arrangement, where both inlet and outlet ends of the channels are open to fluid flow or the structure can be a filter. Various filter arrangements are known, including the so-called wall flow filter, wherein each channel has a plug at one end and the opposite end is open, with any pair of adjacent channels having plugs at opposite channel ends. The term “filter” herein, also includes partial filters, such as those disclosed in EP 1276549 and EP 1057519 (the entire contents of both documents being incorporated herein by reference).
According to a further aspect, the invention provides the use of at least one polysaccharide rheology modifier (as described hereinabove) in the manufacture of a rheologically pseudoplastic washcoat composition for coating a substrate monolith, wherein the washcoat composition comprises a liquid phase and either one or both of (a) suspended metal oxide particles and (b) at least one metal salt solute in the liquid phase, wherein the rheology of the washcoat composition is pseudoplastic.
An aspect of the method disclosed in WO 99/47260 is that each coating step may need to be followed immediately by a drying step and optionally also by a firing (i.e. calcining) step. The use of the polysaccharide rheology modifiers disclosed herein can reduce the number of process steps involved in obtaining the final coated substrate monolith, i.e. they enable a substrate monolith to be part-coated in a first axial direction from one end face, before the part-coated substrate monolith is turned and the remainder of the substrate monolith is coated from the opposite end face in the same axial direction without a drying step between a first washcoat application and a second washcoat application.
The characteristics of rheology modifiers comprising polysaccharide chains that assume rod-like double and particularly triple helices when dissolved—such as scelroglucan, welan gum and diutan gum—are particularly useful in the method disclosed in WO 99/47260. Using these rheology modifiers in particular, it is possible to coat a substrate monolith from one end by application of shear stress using the pressure means and to turn the substrate monolith without first drying the first part-coating before the substrate monolith is coated from the opposite end face. That is, pressure means is applied across an undried first part-coating. One feature of the selected rheology modifiers that facilitates this is that they make the washcoat strongly pseudoplastic, i.e. they can increase in washcoat viscosity rapidly producing a strong gelled-structure (due to triple helical structures of thickeners) with time upon the cessation of the applied shear stress.
Moreover, the use of the above rheology modifiers enables a second washcoat layer to be applied over the dried first washcoat layer, i.e. it may not be necessary first to fire (calcine) the first washcoat layer before overlaying the first washcoat layer with a second washcoat layer. One reason for this is that the drying step sufficiently increases the viscosity of the washcoat composition of the first layer.
The feature that the selected polysaccharide rheology modifiers, e.g. scleroglucan, welan gum and diutan gum, are stable in low pH is also an advantage for washcoating systems that require acid pH, e.g. to impregnate anionic platinum group metal salts onto acidic metal oxide particles, e.g. alumina, silica-alumina and titania. For example, we have seen that relatively low pH washcoat compositions (e.g. less than pH 2.0) containing polysaccharide rheology modifiers that assume a rod-like triple helical structure when dissolved in water retain their viscosity (tested on a Brookfield viscometer) when stored for over two months. This was confirmed for two washcoat compositions, one comprising metal salts (Ce:Zr nitrate) and the other comprising a slurry of metal oxide particles (alumina). It was also observed, that these preferred rheology modifiers are resistant to multivalent cations (such as Ce4+ and Zr4+) at the low pHs tested.
Accordingly, the use of polysaccharide rheology modifiers in general, and these selected rheology modifiers in particular, is advantageous in that they can reduce substantially the number of process steps necessary to obtain a coated substrate monolith.
According to another aspect of the invention, provided is a method for coating a substrate monolith having a plurality of channels and having a first end, wherein said first end comprises a plurality of channel openings, comprising: (a) contacting a predetermined quantity of a rheologically pseudoplastic washcoat with said first end, wherein said washcoat comprises a liquid phase, a polysaccharide rheological modifier, and either one or both of (i) suspended metal oxide particles and (ii) at least one metal salt solute in the liquid phase; (b) applying a vacuum and/or positive pressure to said washcoat, wherein said applying said vacuum and/or positive pressure decreases the viscosity of the washcoat; (c) coating at least a portion of said channels with said washcoat; and (d) removing said vacuum and/or positive pressure from said washcoat. In a particularly preferred embodiment, steps (a), (b), (c), and (d) of this method are performed in the order described above.
According to another aspect, the invention provides a method of coating a substrate monolith comprising a first end face and a second end face and a plurality of substantially parallel channels extending from the first end face to the second end face with a washcoat composition, which method comprising the steps of:
(a) locating a containment means on top of the first end face of the substrate monolith;
(b) dosing a predetermined quantity of a rheologically pseudoplastic washcoat composition comprising a liquid phase, at least one polysaccharide rheology modifier and either one or both of (i) and (ii), wherein (i) is a suspension of metal oxide particles; and (ii) is at least one metal salt solute in the liquid phase into the containment means,
and wherein the order of steps (a) and (b) is (a) then (b) or (b) then (a);
(c) applying pressure to the washcoat composition thereby to generate a shear stress in the washcoat composition and to transfer an entirety of the washcoat composition into the channels of the substrate monolith by plug flow, wherein the predetermined quantity of the washcoat composition is such that substantially all of the predetermined quantity of the washcoat composition is retained within the substrate monolith; and
(d) rotating a part-coated substrate monolith resulting from step (c) so that the second end face is located at the top; and
(e) repeating steps (a) to (c) inclusive without drying the part-coated substrate monolith. It will be appreciated that this method is based on the method disclosed in WO 99/47260 (the entire contents of which is incorporated herein by reference).
According to one method according to the invention, the product of step (e) comprises a substrate monolith coated substantially uniformly with a first layer of the washcoat composition.
The product of step (e) can be subjected to a drying step following which it can be fired (calcined) or alternatively the dried product of step (e) can be coated with a second washcoat layer by repeating steps (a) to (e) inclusive before the two layer product can be fired (calcined).
In embodiments, the washcoat composition comprises a platinum group metal, which can be present as a salt solution or pre-fixed to the metal oxide particles.
Of particular application in this method are polysaccharide rheology modifiers that assume a rod-like triple helical structure when dissolved in water, e.g. Scleroglucan, Diutan gum or Welan gum, for reasons explained hereinabove.
The method according to the invention provides a number of very useful advantages where expensive precious metals are used. These include the more rigorous control of precious metals within the method, reducing losses. For example, the present invention allows washcoat compositions comprising precious metal salts to be applied as a separate step to a washcoat layer(s) containing metal oxide particles that has been laid down in previous step, rather than combining precious metal salts and metal oxide particles in the same washcoat composition (although this is still possible according to the present invention). An advantage is that washcoat compositions comprising precious metal salts and no metal oxide particles are more easily analysed, e.g. using Inductively Coupled Plasma Emission Spectroscopy (ICP-ES) using commercially available standards for solutions, than washcoat compositions comprising precious metal salts and metal oxide particles (“slurries”) where e.g. X-Ray Fluorescence (XRF) can be used, which requires the preparation of “homemade” standards for slurries.
Secondly, since a precious metal application step can be separated from a step of coating the monolith substrate with a washcoat composition containing metal oxide particles, a problem of flushing lines to recover precious metals when the washcoat composition is changed, e.g. from a rhodium containing washcoat composition to a palladium-containing washcoat composition, can be reduced or avoided. There is an economic benefit in that this reduces the amount of time during which production apparatus is inactive while the lines are being flushed (“downtime”). Also there is an environmental advantage in that less rinse water is used for line flushing. The method according to the invention reduces or avoids this problem.
Thirdly, since it is possible to batch production of washcoat compositions that do not contain precious metals, less analysis is required to ensure accuracy of precious metal content to meet specification. Thus, there is a further economic benefit in the amount of work required.
EXAMPLE 1
The viscosities (measured in centipoises or cPs) of solutions of scleroglucan (Actigum CS6 or MMP Clearogel) and guar gum (Viscogum 202) in deionised water (pH 5.0) were determined using a Brookfield Viscometer in 10° C. increments. An illustrative results trend is set out in Tables 1 and 2 and is illustrated in FIGS. 1 and 2.
TABLE 1
Scleroglucan 1.5%: 3 g in
200 ml deionised water
Temperature, ° C. Viscosity
22.8 1000
30.5 1000
40.7 1000
51 1000
61.5 1050
70.9 1000
80.8 1250
90.9 1600
100.1 2400
TABLE 2
Guar Gum - 1%: 2 g in
200 ml deionised water
Temperature, ° C. Viscosity
24.6 1600
30.6 2400
41.6 2600
51.2 2800
60.7 2700
70.5 2600
80.8 2500
91.1 2500
24.6 1600
It can be seen that the viscosity of both these rheology modifiers increases with increasing temperature.
EXAMPLE 2
The viscosity (cPs) of a representative low pH (pH˜0.8) washcoat composition comprising a solution of Ce:Zr nitrate and scleroglucan, guar gum or hydroxyethyl cellulose ((Natrosol MR250) no particulate metal oxide) was tested using a Brookfield Viscometer in 10° C. increments. Illustrative results trends for scleroglucan and hydroxyethyl cellulose are set out in Tables 3 and 4. The results are also shown graphically in FIGS. 3 and 4 respectively. Guar gum would not polymerize in the low pH solution.
TABLE 3
Scleroglucan - 1%: 3 g in
300 g Ce:Zr nitrate solution
Temperature, ° C. Viscosity
24.6 1600
30.6 2400
41.6 2600
51.2 2800
60.7 2700
70.5 2600
80.8 2500
91.1 2500
24.6 1600
TABLE 4
Hydroxyethyl cellulose - 1%:
3 g in 300 g Ce:Zr nitrate solution
Temperature, ° C. Viscosity
22.4 1500
30.5 1400
41.0 1000
50.4 300
60.2 150
70.1 0
80.2 0
90.0 0
EXAMPLE 3
The viscosity (cPs) of a representative washcoat composition containing a particulate metal oxide comprising a colloidal alumina doped with citric acid and platinum nitrate at a pH˜1.5 was tested using a Brookfield Viscometer in 10° C. increments. The illustrative results trend for scleroglucan and guar gum are set out in Tables 5 and 6 and is also shown in FIGS. 5 and 6.
TABLE 5
Scleroglucan - 0.25%: 1 g in 400 g
colloidal alumina; pH 1.47
Temperature, ° C. Viscosity
21.9 3000
30.2 3000
40.1 2400
50.2 2100
60.2 2100
70.2 2600
80.3 2900
90.2 4000
100.1 5400
TABLE 6
Guar gum - 0.125%: 0.5 g in 400 g
colloidal alumina; pH ~1.5
Temperature, ° C. Viscosity
20.7 5100
30.3 4300
40.1 3700
50.6 4200
60.5 4700
70.5 4900
80.1 5000
90.5 5200
100.0 4900
It can be seen that scleroglucan and guar gum worked well for thickening washcoat composition containing particulate metal oxide both at room temperature and when heated to typical drying temperatures. The guar gum showed a decrease in viscosity between 30-50° C., but viscosity recovered at higher temperatures. This was observed on two separate samples with two different concentrations of guar gum (results not shown). Scleroglucan also showed a loss in viscosity between 40-60° C. (results not shown). However, when the test was repeated at a higher polymer concentration, the loss in viscosity was much less pronounced.
EXAMPLE 4
To test the pH tolerance of scleroglucan-containing washcoat compositions, samples from Examples 2 and 3 were stored for several weeks at room temperature and their viscosity was determined intermittently, as set out in Tables 7 and 8.
TABLE 7
Scleroglucan - 1%: 3 g in 300 g
Ce:Zr nitrate solution; pH ~0.8
Date Viscosity
 9th Jul. 2007 3200
12th Jul. 2007 4500
16th Jul. 2007 4000
19th Jul. 2007 5000
24th Jul. 2007 5400
30th Jul. 2007 5600
13th Aug. 2007 5700
12th Sep. 2007 6400
TABLE 8
Scleroglucan - Scleroglucan - 0.25%:
1 g in 400 g colloidal alumina; pH 1.47
Date Viscosity
 9th Jul. 2007 4700
12th Jul. 2007 5000
16th Jul. 2007 5500
19th Jul. 2007 4500
24th Jul. 2007 4800
30th Jul. 2007 4700
13th Aug. 2007 4900
12th Sep. 2007 5100
It can be seen that scleroglucan is a stable rheology modifier in the washcoat composition systems tested.
EXAMPLE 5
Catalysed wall-flow diesel particulate filters having a total length of 12 inches (30.48 cm) were prepared using the method disclosed in WO 99/47260 using the washcoat compositions of Example 2 with the objective of achieving the washcoat component loadings on the catalysed diesel particulate filter set out in Table 9.
TABLE 9
Po- Particulate Pt Ce Zr
si- Metal Oxide (g/ (g/ (g/
tion loading (g/in3) ft3) ft3) ft3) Rheology Modifier %
1 — 500 500 Xanthan (Vanzan ®)
gum 1%
2 — 500 500 Scleroglucan 1%
3 0.35 10 — — Xanthan (Vanzan ®)
gum 0.5%
4 0.35 10 — — Scleroglucan 0.5%
5 0.35 10 — — Guar gum 0.05%
Positions 1 and 2 of 5 in an automated apparatus were prepared targeting 50% dose lengths measured from the top down. The two samples were then transferred into a dryer and dried for 45 minutes at 100° C. These parts were monitored for solution migration using 3-dimensional X-ray throughout the drying process. During drying, the washcoat composition containing xanthan gum migrated from 50% of the filter length down to approximately 75% of the filter length, whereas the scleroglucan-containing sample at position 2 showed virtually no signs of solution migration during the drying step.
Positions 3-5 were prepared using the colloidal alumina washcoat composition of Example #3. A target dose length of 75% of the total length of the filter was intended (approx. 7 inches or 17.78 cm). Samples were dried at 100° C. for 60 minutes and monitored for washcoat migration.
The filter sample at position #3 using xanthan gum began to migrate on heating to the bottom of the filter in a funnel shaped pattern. The centre of the filter showed a 6 inch (15.24 cm) diameter drainage pattern after 30 minutes of drying. After 60 minutes the drainage increased to a 10 inch (25.4 cm) diameter with a 3 inch (7.62 cm) spot which migrated completely through the filter to the opposite end face creating a 3 inch (7.62 cm) diameter spot with cell blockage.
After 30 minutes of drying the position #4 filter sample the centre of the filter showed one ½ inch of washcoat migration. After 60 minutes the part appeared the same, indicating that the washcoat movement was inhibited by the polymerization of the scleroglucan as the internal temperature increased.
After 30 minutes of drying the guar gum-containing sample at position #5, the centre of the filter showed 1 inch (2.54 cm) of washcoat migration. After 60 minutes the washcoat had moved to 8.5 inch (21.59 cm) down the length of the part.
The position #1 sample showed poor thermal stability: gelled solution migration was uncontrolled after the filter temperature exceeded 40° C.
The position #2 sample using scleroglucan as the rheology modifier in Ce:Zr Nitrate solution showed virtually no solution migration during drying up to temperatures of 100° C. Scleroglucan retained its viscosity and inhibited the solution from migrating in a very low pH environment.
Position #3 using xanthan gum showed signs of washcoat migration after several minutes of drying. The washcoat ultimately drained out to the bottom of the part and clogged the cells in the centre of the filter, although the initial viscosity for this position was lower than had been observed prior to the experimental run.
Position #4 with scleroglucan showed minimal washcoat migration after the core temperature of the filter increased during drying. Of the rheology modifiers tested, scleroglucan had the best gelling characteristics at increased temperatures in an acidic medium.
Position #5 using guar gum also showed good rheology characteristics during the drying cycle, although there was more washcoat migration during drying than for the #4 sample, the concentration of guar gum required for colloidal alumina slurries was significantly less than for scleroglucan.
EXAMPLE 6 Tolerance to pH and Multivalent Ions
Nitric acid was added to 600 g of deionised water to lower the pH to 1.2. 266 g of citric acid were then added, resulting in a pH of 1.03. 4.2 g of a commercially available xanthan gum (Vanzan®) were then successively dissolved in the solution. The resulting solution had a viscosity of 2000 cPs (measured by a Brookfield viscometer) and a pH of 1.05.
By contrast, 10.99 g of citric acid were added to 500 g of de-ionised water, followed by 44.26 g of palladium nitrate (13.759% palladium). The resulting pH was 1.1. 6.9 g of xanthan gum were then added. The solution did not thicken as the xanthan did not dissolve but formed a chunk precipitate.

Claims (6)

What is claimed is:
1. A method of coating a substrate monolith comprising a first end face and a second end face and a plurality of substantially parallel channels extending from the first end face to the second end face with a washcoat composition, wherein the method comprises the steps of:
(a) locating a containment means on top of the first end face of the substrate monolith;
(b) dosing a predetermined quantity of a rheologically pseudoplastic washcoat composition comprising a liquid phase, at least one polysaccharide rheology modifier and either one or both of (i) and (ii), wherein (i) is a suspension of metal oxide particles into the containment means; and (ii) is at least one metal salt solute in the liquid phase, and wherein the order of steps (a) and (b) is (a) then (b) or (b) then (a);
(c) applying pressure to the washcoat composition thereby to generate a shear stress in the washcoat composition and to transfer an entirety of the washcoat composition into the channels of the substrate monolith by plug flow, wherein the predetermined quantity of the washcoat composition is such that no more than 1 wt % of the predetermined quantity of the washcoat composition is drawn though the substrate monolith and expelled; and
(d) rotating a part-coated substrate monolith resulting from step (c) so that the second end face is located at the top; and
(e) repeating steps (a) to (c) inclusive without drying the part-coated substrate monolith.
2. A method according to claim 1, wherein a product of step (e) comprises a substrate monolith coated uniformly with a first layer of the washcoat composition.
3. A method according to claim 1, wherein the product of step (e) is subjected to a drying step.
4. A method according to claim 3, wherein the product of step (e) is coated with a second layer of the same or a different washcoat composition by repeating steps (a) to (e) inclusive.
5. A method according to claim 1, wherein the polysaccharide rheology modifier assumes a rod-like triple helical structure when dissolved in water.
6. A method according to claim 1, wherein the polysaccharide rheology modifier is Scleroglucan, Diutan gum or Welan gum.
US12/752,753 2009-04-01 2010-04-01 Method of applying washcoat to monolithic substrate Active 2033-08-28 US9144796B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US12/752,753 US9144796B1 (en) 2009-04-01 2010-04-01 Method of applying washcoat to monolithic substrate

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US16554009P 2009-04-01 2009-04-01
US12/752,753 US9144796B1 (en) 2009-04-01 2010-04-01 Method of applying washcoat to monolithic substrate

Publications (1)

Publication Number Publication Date
US9144796B1 true US9144796B1 (en) 2015-09-29

Family

ID=42983068

Family Applications (1)

Application Number Title Priority Date Filing Date
US12/752,753 Active 2033-08-28 US9144796B1 (en) 2009-04-01 2010-04-01 Method of applying washcoat to monolithic substrate

Country Status (1)

Country Link
US (1) US9144796B1 (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016023808A1 (en) * 2014-08-12 2016-02-18 Umicore Ag & Co. Kg Application of methyl cellulose on washcoats and precious metal solution
US20160129435A1 (en) * 2014-11-11 2016-05-12 Hyundai Motor Company Method for coating catalyst on diesel particulate filter
EP3424596A1 (en) 2017-07-06 2019-01-09 Umicore Ag & Co. Kg Method for coating a monolith carrier
EP3424595A1 (en) 2017-07-06 2019-01-09 Umicore Ag & Co. Kg Coating apparatus and method
WO2019008080A1 (en) 2017-07-06 2019-01-10 Umicore Ag & Co. Kg Method of applying a multilayer wet-on-wet coating to a substrate
KR20200026875A (en) * 2017-07-06 2020-03-11 우미코레 아게 운트 코 카게 Non-contact Leveling of Washcoat Suspensions
EP4299194A1 (en) 2022-06-29 2024-01-03 Umicore AG & Co. KG Coating apparatus

Citations (70)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB765562A (en) 1953-11-18 1957-01-09 Distillers Co Yeast Ltd Improvements in or relating to the production of laminated articles
GB879243A (en) 1958-07-17 1961-10-11 Mendip Chemical Engineering Lt Reinforced plastic
GB907769A (en) 1959-01-27 1962-10-10 Tough Plastics Ltd Improvements in or relating to bonded plastics
GB922924A (en) 1958-07-14 1963-04-03 Claude Lamy Process and machine for the continuous manufacture of reinforced sheet material
GB998240A (en) 1963-10-21 1965-07-14 American Cyanamid Co Rock bolting
US3302410A (en) 1965-10-20 1967-02-07 American Cyanamid Co Rock bolting package usage
US3846442A (en) 1970-11-17 1974-11-05 Ciba Geigy Ag Glycidyl hydantoin compounds
US4465810A (en) 1982-07-01 1984-08-14 The Procter & Gamble Company Agents for preparing cross-linked polymers and water-based paint compositions containing those agents
US4534795A (en) 1983-01-05 1985-08-13 Lewis Christopher G Long shelf life cementitious anchoring capsule
US4609563A (en) * 1985-02-28 1986-09-02 Engelhard Corporation Metered charge system for catalytic coating of a substrate
US4783503A (en) 1985-08-16 1988-11-08 Shell Oil Company Impact resistant blends of thermoplastic polyamides and modified block copolymers
WO1991005085A1 (en) 1989-09-26 1991-04-18 Courtaulds Coatings (Holdings) Limited Improvements related to coatings
US5449732A (en) 1993-06-18 1995-09-12 Conoco Inc. Solvent free oil soluble drag reducing polymer suspension
WO1996036761A2 (en) 1995-05-17 1996-11-21 Nextec Applications, Inc. Controlling the porosity and permeation of a web
WO1996036758A2 (en) 1995-05-17 1996-11-21 Nextec Applications, Inc. Internally-coated porous webs with controlled positioning of modifiers therein
US5696072A (en) * 1995-09-19 1997-12-09 Mcgean-Rohco, Inc. Pseudoplastic, shear thinned paint stripper
US5698303A (en) 1988-03-14 1997-12-16 Nextec Applications, Inc. Controlling the porosity and permeation of a web
US5866210A (en) * 1996-06-21 1999-02-02 Engelhard Corporation Method for coating a substrate
US5953832A (en) * 1998-04-28 1999-09-21 Engelhard Corporation Method for drying a coated substrate
WO1999047260A1 (en) 1998-03-19 1999-09-23 Johnson Matthey Public Limited Company Monolith coating apparatus and method therefor
WO1999048988A1 (en) 1998-03-26 1999-09-30 Merck Patent Gmbh Pigment preparation
WO2000020336A1 (en) 1998-10-07 2000-04-13 Plüss-Staufer Ag Novel rheology regulators such as ground natural calcium carbonates optionally treated with a fatty acid or salt and their use
WO2000037737A1 (en) 1998-12-22 2000-06-29 Bayer Antwerpen N.V. Face-up coating of carpet backs with polyurethane
US6172134B1 (en) 1994-10-15 2001-01-09 British Gas Plc Anaerobically curable composition
WO2001044452A1 (en) 1999-12-15 2001-06-21 Novozymes A/S Subtilase variants having an improved wash performance on egg stains
US6271377B1 (en) 1999-02-25 2001-08-07 Ciba Specialty Chemicals Corporation Hydroxy-substituted N-alkoxy hindered amines and compositions stabilized therewith
US6325884B1 (en) 1999-01-14 2001-12-04 Panolam Industries Abrasion resistant laminate and process for producing same
WO2002064877A2 (en) 2001-01-30 2002-08-22 The Procter & Gamble Company Coating compositions for modifying surfaces
US6478874B1 (en) * 1999-08-06 2002-11-12 Engelhard Corporation System for catalytic coating of a substrate
US20030072694A1 (en) 2000-04-25 2003-04-17 Jan Hodgson Method for removing soot particles from an exhaust gas, associated collecting element and system
GB2385856A (en) 2002-01-15 2003-09-03 Hubdean Ltd Water-based, fire retarding coating composition
WO2003085039A1 (en) 2002-04-10 2003-10-16 Ciba Specialty Chemicals Holding Inc. Flame retardant coatings
US6652915B1 (en) 1999-05-25 2003-11-25 Basf Coatings Ag Coating material containing a mixture of silicic acids and urea and/or urea derivatives
US20040002559A1 (en) 2002-04-10 2004-01-01 Malisa Troutman Flame retardant coatings
WO2004046214A2 (en) 2002-10-15 2004-06-03 Exxonmobil Chemical Patents Inc. Multiple catalyst system for olefin polymerization and polymers produced therefrom
DE10303651A1 (en) 2003-01-27 2004-08-05 Deutsches Zentrum für Luft- und Raumfahrt e.V. Washcoat dispersion solution, for coating support with carrier material, used in heterogeneous catalysis, has metal oxide nanoparticles as carrier material
WO2006002935A1 (en) 2004-07-03 2006-01-12 Construction Research & Technology Gmbh Mixture composition containing unsaturated carboxylic acid and alkene ether derivative based copolymers and copolymers and terpolymers containing sulfo groups and use thereof
WO2006084523A1 (en) 2005-02-11 2006-08-17 Degussa Gmbh Aqueous compositions
US20060197056A1 (en) 2005-03-01 2006-09-07 Martin Roy W Solvent-activated reactor using colloidal gel
WO2006094849A1 (en) 2005-03-10 2006-09-14 Degussa Gmbh Aqueous coating substance compositions for decorative paint effects
US20070129528A1 (en) 2005-12-01 2007-06-07 Misty Huang Two-part curable composition and polyurethane-polysiloxane resin mixture obtained therefrom
US7241410B2 (en) 2003-02-12 2007-07-10 Opera Laboratori Fiorentini S.P.A. Process for making a product of artificial rock
WO2007077057A1 (en) 2006-01-03 2007-07-12 Degussa Ag Compositions for universal use
EP1057519B1 (en) 1999-05-18 2007-08-01 Ecocat OY Purification system for diesel engine exhaust gases
US20070179242A1 (en) 2006-02-01 2007-08-02 Landon Shoyne J Sealant composition having reduced permeability to gas
US20070256736A1 (en) * 2006-04-20 2007-11-08 Anna Lee Tonkovich Process for treating and/or forming a non-newtonian fluid using microchannel process technology
US20080069949A1 (en) 2006-09-15 2008-03-20 Degussa Gmbh Silane-functional, chlorine-free composition
US20080145625A1 (en) 2005-08-03 2008-06-19 Jorg Schumacher Substrate, including at least one full or partial surface macro-structured layer, method for producing same and its application
US20080262144A1 (en) 2004-10-19 2008-10-23 Degussa Gmbh Aqueous, Radiation-Hardenable Resins, Method for the Production Thereof, and Use of the Same
WO2008154011A1 (en) 2007-06-11 2008-12-18 Textile Rubber & Chemical Company, Inc. Novel polyurethane compositions including castor oil
US20090035506A1 (en) 2007-06-01 2009-02-05 Sika Technology Ag Honeycomb sandwich panels and the use of a two component polyrethane adhesive in the manufacture thereof
US7521087B2 (en) * 2002-08-27 2009-04-21 Basf Catalysts Llc Method for catalyst coating of a substrate
US20090160091A1 (en) 2005-07-19 2009-06-25 Cummins Turbo Technologies Limited Method and apparatus for manufacturing turbine or compressor wheels
US20090227732A1 (en) 2004-10-26 2009-09-10 Degussa Gmbh Use of an aqueous dispersion based on an unsaturated, amorphous polyester based on defined dicidol isomers
US7678416B2 (en) * 2005-12-05 2010-03-16 Cataler Corporation Substrate coating method
US20100208429A1 (en) 2007-09-14 2010-08-19 Yimin Zhang Thermally Conductive Composition
US20100233146A1 (en) 2002-09-09 2010-09-16 Reactive Surfaces, Ltd. Coatings and Surface Treatments Having Active Enzymes and Peptides
US7837890B2 (en) 2005-01-11 2010-11-23 Merck Patent Gmbh Printable medium for the etching of silicon dioxide and silicon nitride layers
WO2011005214A1 (en) 2009-07-10 2011-01-13 Milux Holding S.A. Hip joint device and method
US20110042004A1 (en) 2009-08-19 2011-02-24 Evonik Goldschmidt Gmbh Curable material comprising silylated polymers containing urethane groups, and use thereof in sealants, adhesives, binders and/or surface modifiers
US20110054042A1 (en) * 2009-09-01 2011-03-03 Rhodia Operations Polymer compositions
US8088297B2 (en) 2005-07-12 2012-01-03 Merck Patent Gmbh Combined etching and doping media for silicon dioxide layers and underlying silicon
US20120129995A1 (en) 2009-07-29 2012-05-24 Basf Se Encapsulated phenolic antioxidants
US20120251832A1 (en) 2011-03-31 2012-10-04 Momentive Performance Materials Inc. Moisture Curable Silylated Polymer Compositions With Improved Adhesion to Concrete
WO2013059479A2 (en) 2011-10-19 2013-04-25 Bioformix Inc. Methylene beta-diketone monomers, methods for making methylene beta-diketone monomers, polymerizable compositions and products formed therefrom
US20130281580A1 (en) 2010-10-20 2013-10-24 Bioformix Inc. Synthesis of methylene malonates using rapid recovery in the presence of a heat transfer agent
US8574670B2 (en) * 2007-03-29 2013-11-05 Corning Incorporated Method for membrane deposition
US20130309448A1 (en) 2010-09-11 2013-11-21 Bayer Intellectual Property Gmbh Coating based on polyurethane for display regions
US8703236B2 (en) * 2010-01-04 2014-04-22 Johnson Matthey Public Limited Company Coating a monolith substrate with catalyst component
US8863685B2 (en) * 2010-12-07 2014-10-21 Sumitomo Chemical Company, Limited Device for conveying honeycomb structural body, method for sealing honeycomb structural body, and method for producing honeycomb structural body

Patent Citations (72)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB765562A (en) 1953-11-18 1957-01-09 Distillers Co Yeast Ltd Improvements in or relating to the production of laminated articles
GB922924A (en) 1958-07-14 1963-04-03 Claude Lamy Process and machine for the continuous manufacture of reinforced sheet material
GB879243A (en) 1958-07-17 1961-10-11 Mendip Chemical Engineering Lt Reinforced plastic
GB907769A (en) 1959-01-27 1962-10-10 Tough Plastics Ltd Improvements in or relating to bonded plastics
GB998240A (en) 1963-10-21 1965-07-14 American Cyanamid Co Rock bolting
US3302410A (en) 1965-10-20 1967-02-07 American Cyanamid Co Rock bolting package usage
US3846442A (en) 1970-11-17 1974-11-05 Ciba Geigy Ag Glycidyl hydantoin compounds
US4465810A (en) 1982-07-01 1984-08-14 The Procter & Gamble Company Agents for preparing cross-linked polymers and water-based paint compositions containing those agents
US4534795A (en) 1983-01-05 1985-08-13 Lewis Christopher G Long shelf life cementitious anchoring capsule
US4609563A (en) * 1985-02-28 1986-09-02 Engelhard Corporation Metered charge system for catalytic coating of a substrate
US4783503A (en) 1985-08-16 1988-11-08 Shell Oil Company Impact resistant blends of thermoplastic polyamides and modified block copolymers
US5869172A (en) 1988-03-14 1999-02-09 Nextec Applications, Inc. Internally-coated porous webs with controlled positioning of modifiers therein
US5698303A (en) 1988-03-14 1997-12-16 Nextec Applications, Inc. Controlling the porosity and permeation of a web
WO1991005085A1 (en) 1989-09-26 1991-04-18 Courtaulds Coatings (Holdings) Limited Improvements related to coatings
US5449732A (en) 1993-06-18 1995-09-12 Conoco Inc. Solvent free oil soluble drag reducing polymer suspension
US6172134B1 (en) 1994-10-15 2001-01-09 British Gas Plc Anaerobically curable composition
WO1996036761A2 (en) 1995-05-17 1996-11-21 Nextec Applications, Inc. Controlling the porosity and permeation of a web
WO1996036758A2 (en) 1995-05-17 1996-11-21 Nextec Applications, Inc. Internally-coated porous webs with controlled positioning of modifiers therein
US5696072A (en) * 1995-09-19 1997-12-09 Mcgean-Rohco, Inc. Pseudoplastic, shear thinned paint stripper
US5866210A (en) * 1996-06-21 1999-02-02 Engelhard Corporation Method for coating a substrate
WO1999047260A1 (en) 1998-03-19 1999-09-23 Johnson Matthey Public Limited Company Monolith coating apparatus and method therefor
WO1999048988A1 (en) 1998-03-26 1999-09-30 Merck Patent Gmbh Pigment preparation
US5953832A (en) * 1998-04-28 1999-09-21 Engelhard Corporation Method for drying a coated substrate
WO2000020336A1 (en) 1998-10-07 2000-04-13 Plüss-Staufer Ag Novel rheology regulators such as ground natural calcium carbonates optionally treated with a fatty acid or salt and their use
WO2000037737A1 (en) 1998-12-22 2000-06-29 Bayer Antwerpen N.V. Face-up coating of carpet backs with polyurethane
US6325884B1 (en) 1999-01-14 2001-12-04 Panolam Industries Abrasion resistant laminate and process for producing same
US6271377B1 (en) 1999-02-25 2001-08-07 Ciba Specialty Chemicals Corporation Hydroxy-substituted N-alkoxy hindered amines and compositions stabilized therewith
EP1057519B1 (en) 1999-05-18 2007-08-01 Ecocat OY Purification system for diesel engine exhaust gases
US6652915B1 (en) 1999-05-25 2003-11-25 Basf Coatings Ag Coating material containing a mixture of silicic acids and urea and/or urea derivatives
US6478874B1 (en) * 1999-08-06 2002-11-12 Engelhard Corporation System for catalytic coating of a substrate
WO2001044452A1 (en) 1999-12-15 2001-06-21 Novozymes A/S Subtilase variants having an improved wash performance on egg stains
US20030072694A1 (en) 2000-04-25 2003-04-17 Jan Hodgson Method for removing soot particles from an exhaust gas, associated collecting element and system
EP1276549B1 (en) 2000-04-25 2005-06-15 Emitec Gesellschaft für Emissionstechnologie mbH Method for removing soot particles from an exhaust gas and corresponding collecting element
WO2002064877A2 (en) 2001-01-30 2002-08-22 The Procter & Gamble Company Coating compositions for modifying surfaces
GB2385856A (en) 2002-01-15 2003-09-03 Hubdean Ltd Water-based, fire retarding coating composition
WO2003085039A1 (en) 2002-04-10 2003-10-16 Ciba Specialty Chemicals Holding Inc. Flame retardant coatings
US20040002559A1 (en) 2002-04-10 2004-01-01 Malisa Troutman Flame retardant coatings
US7521087B2 (en) * 2002-08-27 2009-04-21 Basf Catalysts Llc Method for catalyst coating of a substrate
US20100233146A1 (en) 2002-09-09 2010-09-16 Reactive Surfaces, Ltd. Coatings and Surface Treatments Having Active Enzymes and Peptides
WO2004046214A2 (en) 2002-10-15 2004-06-03 Exxonmobil Chemical Patents Inc. Multiple catalyst system for olefin polymerization and polymers produced therefrom
DE10303651A1 (en) 2003-01-27 2004-08-05 Deutsches Zentrum für Luft- und Raumfahrt e.V. Washcoat dispersion solution, for coating support with carrier material, used in heterogeneous catalysis, has metal oxide nanoparticles as carrier material
US7241410B2 (en) 2003-02-12 2007-07-10 Opera Laboratori Fiorentini S.P.A. Process for making a product of artificial rock
WO2006002935A1 (en) 2004-07-03 2006-01-12 Construction Research & Technology Gmbh Mixture composition containing unsaturated carboxylic acid and alkene ether derivative based copolymers and copolymers and terpolymers containing sulfo groups and use thereof
US20080262144A1 (en) 2004-10-19 2008-10-23 Degussa Gmbh Aqueous, Radiation-Hardenable Resins, Method for the Production Thereof, and Use of the Same
US20090227732A1 (en) 2004-10-26 2009-09-10 Degussa Gmbh Use of an aqueous dispersion based on an unsaturated, amorphous polyester based on defined dicidol isomers
US7837890B2 (en) 2005-01-11 2010-11-23 Merck Patent Gmbh Printable medium for the etching of silicon dioxide and silicon nitride layers
WO2006084523A1 (en) 2005-02-11 2006-08-17 Degussa Gmbh Aqueous compositions
US20060197056A1 (en) 2005-03-01 2006-09-07 Martin Roy W Solvent-activated reactor using colloidal gel
WO2006094849A1 (en) 2005-03-10 2006-09-14 Degussa Gmbh Aqueous coating substance compositions for decorative paint effects
US8088297B2 (en) 2005-07-12 2012-01-03 Merck Patent Gmbh Combined etching and doping media for silicon dioxide layers and underlying silicon
US20090160091A1 (en) 2005-07-19 2009-06-25 Cummins Turbo Technologies Limited Method and apparatus for manufacturing turbine or compressor wheels
US20080145625A1 (en) 2005-08-03 2008-06-19 Jorg Schumacher Substrate, including at least one full or partial surface macro-structured layer, method for producing same and its application
US20070129528A1 (en) 2005-12-01 2007-06-07 Misty Huang Two-part curable composition and polyurethane-polysiloxane resin mixture obtained therefrom
US7678416B2 (en) * 2005-12-05 2010-03-16 Cataler Corporation Substrate coating method
WO2007077057A1 (en) 2006-01-03 2007-07-12 Degussa Ag Compositions for universal use
US20070179242A1 (en) 2006-02-01 2007-08-02 Landon Shoyne J Sealant composition having reduced permeability to gas
US20070256736A1 (en) * 2006-04-20 2007-11-08 Anna Lee Tonkovich Process for treating and/or forming a non-newtonian fluid using microchannel process technology
US20080069949A1 (en) 2006-09-15 2008-03-20 Degussa Gmbh Silane-functional, chlorine-free composition
US8574670B2 (en) * 2007-03-29 2013-11-05 Corning Incorporated Method for membrane deposition
US20090035506A1 (en) 2007-06-01 2009-02-05 Sika Technology Ag Honeycomb sandwich panels and the use of a two component polyrethane adhesive in the manufacture thereof
WO2008154011A1 (en) 2007-06-11 2008-12-18 Textile Rubber & Chemical Company, Inc. Novel polyurethane compositions including castor oil
US20100208429A1 (en) 2007-09-14 2010-08-19 Yimin Zhang Thermally Conductive Composition
WO2011005214A1 (en) 2009-07-10 2011-01-13 Milux Holding S.A. Hip joint device and method
US20120129995A1 (en) 2009-07-29 2012-05-24 Basf Se Encapsulated phenolic antioxidants
US20110042004A1 (en) 2009-08-19 2011-02-24 Evonik Goldschmidt Gmbh Curable material comprising silylated polymers containing urethane groups, and use thereof in sealants, adhesives, binders and/or surface modifiers
US20110054042A1 (en) * 2009-09-01 2011-03-03 Rhodia Operations Polymer compositions
US8703236B2 (en) * 2010-01-04 2014-04-22 Johnson Matthey Public Limited Company Coating a monolith substrate with catalyst component
US20130309448A1 (en) 2010-09-11 2013-11-21 Bayer Intellectual Property Gmbh Coating based on polyurethane for display regions
US20130281580A1 (en) 2010-10-20 2013-10-24 Bioformix Inc. Synthesis of methylene malonates using rapid recovery in the presence of a heat transfer agent
US8863685B2 (en) * 2010-12-07 2014-10-21 Sumitomo Chemical Company, Limited Device for conveying honeycomb structural body, method for sealing honeycomb structural body, and method for producing honeycomb structural body
US20120251832A1 (en) 2011-03-31 2012-10-04 Momentive Performance Materials Inc. Moisture Curable Silylated Polymer Compositions With Improved Adhesion to Concrete
WO2013059479A2 (en) 2011-10-19 2013-04-25 Bioformix Inc. Methylene beta-diketone monomers, methods for making methylene beta-diketone monomers, polymerizable compositions and products formed therefrom

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016023808A1 (en) * 2014-08-12 2016-02-18 Umicore Ag & Co. Kg Application of methyl cellulose on washcoats and precious metal solution
US20160129435A1 (en) * 2014-11-11 2016-05-12 Hyundai Motor Company Method for coating catalyst on diesel particulate filter
EP3424596A1 (en) 2017-07-06 2019-01-09 Umicore Ag & Co. Kg Method for coating a monolith carrier
EP3424595A1 (en) 2017-07-06 2019-01-09 Umicore Ag & Co. Kg Coating apparatus and method
WO2019008078A1 (en) 2017-07-06 2019-01-10 Umicore Ag & Co. Kg Method for coating a monolith carrier
WO2019008076A1 (en) 2017-07-06 2019-01-10 Umicore Ag & Co. Kg Coating apparatus and method
WO2019008080A1 (en) 2017-07-06 2019-01-10 Umicore Ag & Co. Kg Method of applying a multilayer wet-on-wet coating to a substrate
US10183287B1 (en) * 2017-07-06 2019-01-22 Umicore Ag & Co. Kg Method of applying a multilayer wet-on-wet coating to a substrate
CN110769932A (en) * 2017-07-06 2020-02-07 优美科股份公司及两合公司 Method for applying a multi-layer wet-on-wet coating to a substrate
KR20200026875A (en) * 2017-07-06 2020-03-11 우미코레 아게 운트 코 카게 Non-contact Leveling of Washcoat Suspensions
KR20200026976A (en) * 2017-07-06 2020-03-11 우미코레 아게 운트 코 카게 How to Apply a Multilayer Wet-on-Wet Coating to a Substrate
JP2020525265A (en) * 2017-07-06 2020-08-27 ユミコア・アクチエンゲゼルシャフト・ウント・コムパニー・コマンディットゲゼルシャフトＵｍｉｃｏｒｅ ＡＧ ＆ Ｃｏ．ＫＧ Method of applying a multi-layer wet-on-wet coating to a substrate
US11141720B2 (en) 2017-07-06 2021-10-12 Umicore Ag & Co. Kg Coating apparatus and method
US11590484B2 (en) 2017-07-06 2023-02-28 Umicore Ag & Co. Kg Contactless leveling of a washcoat suspension
CN110769932B (en) * 2017-07-06 2023-03-14 优美科股份公司及两合公司 Method for applying a multi-layer wet-on-wet coating to a substrate
EP4299194A1 (en) 2022-06-29 2024-01-03 Umicore AG & Co. KG Coating apparatus

Similar Documents

Publication Publication Date Title
US9144796B1 (en) Method of applying washcoat to monolithic substrate
Fu et al. Effect of hydrocolloids and salts on retrogradation of native and modified maize starch
US5362312A (en) Carrier fluid for the suspension and delivery of water soluble polymers
US5552462A (en) Compositions including cationic polymers and anionic xanthan gum
EP1833904B1 (en) Water-dispersible xanthan gum containing composition
WO2006013190A1 (en) Fast dissolving hydroxyalkyl guar derivatives
CN103261233A (en) Novel cellulose ethers and their use
WO2011120533A1 (en) New high viscosity carboxymethyl cellulose and method of preparation
CN105102556B (en) The water-soluble polysaccharide that palatability improves
Liu et al. Effects of soluble dietary fiber on the crystallinity, pasting, rheological, and morphological properties of corn resistant starch
CN102259900B (en) Hydrated alumina and preparation method thereof
Ortega-Ojeda et al. Gel formation in mixtures of hydrophobically modified potato and high amylopectin potato starch
CN101942320A (en) Method for producing base oil by isodewaxing
Yanping et al. Cross-linking of partially hydrolyzed sesbania gum, property and characterization
AU2005232246B2 (en) Method of increasing the low shear rate viscosity of well drilling and servicing fluids containing calcined magnesia bridging solids, the fluids and methods of use
EP1490410B1 (en) Building additives based on purified hydrophobically modified hydroxyalkyl guar
CN103012613B (en) A kind of preparation method of cationic polysaccharide tamarind
EP2475686B1 (en) Microprocessing in heterogeneous reaction mixtures
JP2014240538A (en) Method for manufacturing composite of metal nanoparticles and cellulose-based fiber
EP4173702A1 (en) Polymaleic acid assisted metal nanoparticle synthesis for three-way catalysis application
Muhamedbegović et al. Modification of potato starch
CN110256594B (en) Non-ionic cassia seed polysaccharide derivative and preparation method and application thereof
CN107502227A (en) A kind of non-ionic starch based adhesive and preparation method thereof
CN115490882A (en) Temperature response type gel plugging agent and preparation method and application thereof
CN113845894B (en) Low-pyruvyl xanthan gum-based temperature-resistant polymer and application thereof

Legal Events

Date Code Title Description
AS Assignment

Owner name: JOHNSON MATTHEY PUBLIC LIMITED COMPANY, UNITED KIN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BENNETT, CHRISTOPHER JOHN;COLL, JOHN P.;DE, DEBNATH;AND OTHERS;SIGNING DATES FROM 20100518 TO 20100609;REEL/FRAME:024573/0841

STCF Information on status: patent grant

Free format text: PATENTED CASE

MAFP Maintenance fee payment

Free format text: PAYMENT OF MAINTENANCE FEE, 4TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1551); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

Year of fee payment: 4

MAFP Maintenance fee payment

Free format text: PAYMENT OF MAINTENANCE FEE, 8TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1552); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

Year of fee payment: 8